1. Field of the Invention
This invention relates to a display device for use in a viewfinder of a camera-integrated type VTR or the like.
2. Description of the Related Art
FIG. 1 is a block diagram showing the arrangement of the conventional camera-integrated type VTR (video tape recorder). Referring to FIG. 1, a lens 1 is arranged to form an image of an object of shooting. An iris 2 is composed of iris blades arranged to adjust the quantity of incident light. An image sensor 3 which is a CCD or the like is arranged to photo-electrically convert into a video signal an image which is formed by the lens 1 and the quantity of light of which is adjusted by the iris 2. An automatic gain control circuit (hereinafter referred to as an AGC circuit) 4 is arranged to electrically amplify the video signal outputted from the image sensor 3. A video signal processing circuit 5 is arranged to convert the video signal into a standardized video signal by carrying out a predetermined signal processing action on the video signal. A video tape recorder (abbreviated to VTR) part 6 is arranged to record the video signal on a tape. A moving direction selecting circuit 7 is arranged to move the display position of an index or area which is provided for selection of a part of the video signal (hereinafter referred to as a "selection frame") in the direction intended by the operator of the VTR in response to an input from such input means as a joy stick, a track ball, a mouse, a touch panel or the like. A position designating circuit 8 is arranged to designate a display position of the above-stated selection frame with respect to the moving direction selected by the moving direction selecting circuit 7. The position designating circuit 8 is composed of a microcomputer disposed within the camera part of the VTR. A display signal forming circuit 9 is arranged to form a selection frame display signal for displaying the selection frame in a position designated by the position designating circuit 8. A signal adding circuit 10 is arranged to add the selection frame display signal to the video signal to obtain a sum signal. An electric viewfinder (abbreviated to EVF) 11 is arranged as a monitor device for allowing the operator to monitor the sum signal obtained by the signal adding circuit.
FIG. 2 shows a selection frame 111 which is displayed on an image plane of the EVF 11. The selection frame 111 is provided for selecting an area to be used for distance measurement or light measurement on the image plane 110 of the EVF 11 in carrying out automatic focusing (AF) or an automatic exposure (AE). In this example, the selection frame 111 is arranged to permit selection, by the moving direction selecting circuit 7, of any of eight directions which differ from each other by 45 degrees as shown in FIG. 2.
The conventional camera-integrated type VTR operates as follows. Referring to FIG. 1, an optical image obtained by the image forming lens 1 is photo-electrically converted into a video signal by the image sensor 3 through the iris 2. After photo-electric conversion, the video signal is amplified by the AGC circuit 4. The amplified video signal is sent to the video signal processing circuit 5. At the video signal processing circuit 5, the video signal is subjected to various processes such as gamma correction, color separation and color-difference matrixing processes. After these processes, synchronizing signals are added to the video signal to convert the video signal into a standard TV signal. The TV signal is supplied to the VTR part 6, where the TV signal is recorded on a tape.
One of the eight moving directions of the selection frame 111 is selected by the moving direction selecting circuit 7. The position designating circuit 8 determines the display position of the selection frame 111 and the selection frame 111 is moved accordingly. At the display signal forming circuit 9, a selection frame display signal for displaying the selection frame 111 in the display position determined by the position designating circuit 8 is formed and applied to the signal adding circuit 10. At the signal adding circuit 10, the selection frame display signal from the display signal forming circuit 9 is added to the video signal from the video signal processing circuit 5 to obtain a sum signal. The sum signal thus obtained is supplied to the EVF 11 to be displayed there. The EVF 11 then permits the operator to monitor the selection frame 111 along with a video image.
Referring to FIGS. 3(a) to 3(f), in a case where a moving direction is selected by the moving direction selecting circuit 7, for example, for an "obliquely upward direction to the right" to move the selection frame 111 from a left lower end to a right upper end on the image plane 110 of the EVF 11, the VTR operates as follows. It is to be noted that the aspect ratio of the image plane 110 of the EVF 11 shown in FIGS. 3(a) to 3(f) is 4:3.
Assume that the selection frame 111 is placed in a position (1) as shown in FIG. 3(a) before the commencement of moving the selection frame 111. Further, assume that the moving direction selecting circuit 7 is caused to select a "45.degree. obliquely upward direction to the right" as a moving direction and that the selection frame 111 is moved in that moving direction. FIG. 3(b) shows a locus of movement of the selection frame 111 from the position (1) to another position (2). In this instance, the selection frame 111 is thus moved in the "45.degree. obliquely upward direction to the right", which is a moving direction selected by the moving direction selecting circuit 7. FIG. 3(c) shows a locus of movement of the selection frame 111 from the position (2) to a position (3). As the selection frame 111 is caused to continue its movement in the "45.degree. obliquely upward direction to the right" in this manner, the selection frame 111 comes to a stop when the upper side of the selection frame 111 impinges on the upper side of the image plane 110. If it is desired to further move the selection frame 111 from this position up to the right upper end of the image plane 110, the moving direction selecting circuit 7 is caused to select a "horizontal direction to the right" as a moving direction. FIG. 3(d) shows a locus of movement of the selection frame 111 from the position (3) to a position (4). FIG. 3(e) shows a locus of further movement of the selection frame 111 from the position (4) to a position (5). As the selection frame 111 is allowed to continue its movement in the "horizontal direction to the right" in this manner, the right side of the selection frame 111 comes to impinge on the right side of the image plane 110. The selection frame 111 then comes to a stop at the right upper end (5), as shown in FIG. 3(f). In this position, the upper side of the selection frame 111 coincides with the upper side of the image plane 110 and the right side of the selection frame 111 coincides with the right side of the image plane 110. It is, therefore, impossible to move the selection frame 111 any further even if an instruction is given for moving the selection frame 111 in the "horizontal direction to the right". The selection frame 111 thus can be moved up to the right upper end part of the image plane 110.
In the display device of the camera-integrated type VTR described above, a movement of the selection frame 111 in the moving direction selected by the moving direction selecting circuit 7, however, has presented a problem, which is as follows. For example, in moving the selection frame 111 from the left lower end to the right upper end of the image plane 110 having the aspect ratio of 4:3 in the TV viewfinder, as shown in FIGS. 3(a) to 3(f), a locus of movement of the selection frame 111 is such that the selection frame 111 first comes to the upper side of the image plane 110 and, after that, reaches the right upper end by moving in the horizontal direction to the right. Such a locus of movement of the selection frame 111 is not only disadvantageous in terms of operability for the operator but also degrades the quality of the display device as the movement appears to be unnatural.